Small-Block Top-End Swap - Big Power For Little Cash

Swapping Top-End Parts to Make 523 Horses

Step By Step

It's all about flow, babyFor our testing we used the new AFR 195 Street Eliminator cylinder heads on our 388 small-block. The final compression ratio using these heads is about 10.6:1 so 91-octane fuel is required for operation.

The ports in the Eliminator heads are shaped to achieve good velocity through a relatively small cross-sectional port. This design promotes strong low- and midlift flow numbers, while still achieving a high peak flow number. Although the heads are initially designed by hand and lots of experience, the final product is completely reproduced on a CNC machine. This production method ensures that all of the ports flow the exact amount of air with the same velocity.

Let It FlowFor a quick reference we've listed the flow data from the original street heads against the new Eliminator versions. It's important to point out that even the previous cylinder heads produced solid flow numbers when measured against others in the aftermarket, and the new versions take it over the top. Note that the new head flows 278 cfm at 0.500 inch lift, which is important because most serious street cams have maximum lift just past the 0.500-inch point.

For our baseline run we ran the Edelbrock Performer RPM Air Gap intake manifold. This manifold is a dual-plane intake and provided the highest torque numbers. For the remainder of the testing we ran the Edelbrock Victor Jr., an open-plenum intake, for our highest peak-horsepower figures. Airflow below the plenum on either manifold keeps the intake charge cooler and denser for added power.

To free even more power, the Eliminator head uses lightweight 8mm stem valves, retainers, and locks. With both intake and exhaust considered, each cylinder has shed 103 grams. The lighter the valvetrain, the more accurate the valve motion control at high rpm. This simple change allows an engine to continue operation higher in the rpm band, while delivering added horsepower.

The mission: Take a purse of about $2,750, a willing 388ci small-block, and make over 500 hp by adding some of the industry's best top-end bolt-on performance parts. To fulfill this tall but doable order requires an exceptional set of cylinder heads, a well-thought-out camshaft design, and an intake manifold to supply the engine with sufficient airflow. As you already know, more air means more power.

Cylinder-head technology has advanced light-years from what was available only a generation ago. This is largely thanks to the combination of several key factors including lighter-weight components and flatter, more efficient valve angles formerly associated with high-end race stuff, producing the most efficient power measured under the curve.

Suffice to say, Air Flow Research (AFR) has been very busy staying ahead of the cylinder-head development curve, as evidenced by the recently released Eliminator series, an all-new cylinder head for street or competition that increases flow numbers significantly over any previous design. This new benchmark has been accomplished by completely redesigning the combustion chamber, ports, throat area, and valve job on a 23-degree head, creating a greatly improved cylinder head from top to bottom-with the flow numbers to prove it. At 0.500 inch lift this head flows an impressive 278 cfm on the intake side, which is a 17 cfm increase compared with the original design, which flowed less (though still respectable at 260 cfm). For even more power, you can expect a competition version by the time you read this.

Of course, when we first learned about the Eliminator heads, we had to see how well they would perform. Lucky for us, we're in pretty tight with AFR's cylinder-head guru, Tony Mamo, and we managed to bug him into letting us test a pair, but not just any pair; we actually got the very first pair. After describing our test mule, and at Mamo's recommendation, we opted to try out the larger 195 version over the 180s and set a date to meet him at the Westech Dyno facility, where we spent the entire day flogging his latest creation on our trusty small-block 388. A quick one-time pull wouldn't do anyone any justice, so we tested them in several configurations that included two Comp Cams camshafts (XE274H and XE284H), an Edelbrock Performer RPM Air Gap and an Edelbrock Victor Jr. intake, and two sets of Pro Magnum roller rockers (1.52 and 1.6 ratios). By the end of the day, we had made an unimaginable number of dyno runs and had our story. From mild to slightly wilder, we show two distinctly different combinations that both made incredible power; however, if you opt for the slightly more aggressive configuration shown here you can actually expect to save a cool $20. Check out the details, and be sure to e-mail us at chevyhi@sourceinterlink.com and let us know which combination is your favorite.

QUICK NOTES

What we didDyno-flog AFR's latest 195 Eliminator street heads, show the difference in gains between the Edelbrock RPM & Victor Jr. manifold, and push the limits with two camshaft grinds from Comp Cams.

What we didDyno-flog AFR's latest 195 Eliminator street heads, show the difference in gains between the Edelbrock RPM & Victor Jr. manifold, and push the limits with two camshaft grinds from Comp Cams.

Price (APPROX)$2,750 in top-end parts (not including carb)

The new head is the result of intense research and development into the new Eliminator series. Mamo tells us that when he designs a new head like the 195 Eliminator, he begins at the combustion chamber, works his way up to the valve job, then tackles the ports. The combustion chamber's shape is critical to flow because it helps shape the umbrella of air coming off the intake valve, and helps direct the air into the exhaust port. The process of designing a performance cylinder head is largely rooted in old-fashioned trial-and-error, shaping almost everything by hand and using some epoxy. Only then is the finished product's final design digitally programmed so that it can be recreated to other cylinder heads on a CNC machine.

For our baseline test we achieved the highest torque of the day, 490 lb-ft at 4,400 rpm. This is largely due to three reasons: The XE274H camshaft features less duration, the Air Gap intake is a dual-plane manifold, which helps produce a stronger intake signal, and the 750-cfm carburetor is comparatively smaller than the larger 850 we later used.

For this test we switched intakes from the Performer RPM Air Gap (dual-plane) to the Victor Jr. (single-plane) and recorded improved horsepower at a 200 higher engine rpm (488 hp at 5,900 rpm, compared with Test 1's 471 hp at 5,700 rpm). The peak torque number dropped to 475 lb-ft but at a slightly higher rpm.

Finally, we added an S&B 4x15-inch air filter, fired up the dyno, and recorded 523 hp. A number of variables can account for the increase, but the point to drive home is that the filter certainly didn't hurt the performance.

It's all about flow, babyFor our testing we used the new AFR 195 Street Eliminator cylinder heads on our 388 small-block. The final compression ratio using these heads is about 10.6:1 so 91-octane fuel is required for operation.

The ports in the Eliminator heads are shaped to achieve good velocity through a relatively small cross-sectional port. This design promotes strong low- and midlift flow numbers, while still achieving a high peak flow number. Although the heads are initially designed by hand and lots of experience, the final product is completely reproduced on a CNC machine. This production method ensures that all of the ports flow the exact amount of air with the same velocity.

Let It FlowFor a quick reference we've listed the flow data from the original street heads against the new Eliminator versions. It's important to point out that even the previous cylinder heads produced solid flow numbers when measured against others in the aftermarket, and the new versions take it over the top. Note that the new head flows 278 cfm at 0.500 inch lift, which is important because most serious street cams have maximum lift just past the 0.500-inch point.

For our baseline run we ran the Edelbrock Performer RPM Air Gap intake manifold. This manifold is a dual-plane intake and provided the highest torque numbers. For the remainder of the testing we ran the Edelbrock Victor Jr., an open-plenum intake, for our highest peak-horsepower figures. Airflow below the plenum on either manifold keeps the intake charge cooler and denser for added power.

To free even more power, the Eliminator head uses lightweight 8mm stem valves, retainers, and locks. With both intake and exhaust considered, each cylinder has shed 103 grams. The lighter the valvetrain, the more accurate the valve motion control at high rpm. This simple change allows an engine to continue operation higher in the rpm band, while delivering added horsepower.

We ran tests 1-3 with a 750-cfm Mighty Demon carb, and 4-6 with an 850-cfm Mighty Demon carb, both featuring mechanical secondaries.

Our smaller cam teamed with the dual-plane intake and smaller 750 Mighty Demon produced the most torque, measuring 490 lb-ft at 4,400 rpm.

For tests 3-6 we swapped out the 1.52 Pro Magnum roller rockers to a higher 1.60:1 ratio and effectively changed the lift upward from 0.514- to 0.540-inch.

The 1.60:1-ratio Pro Magnum roller rockers also used a larger 7/16-inch stud (instead of 3/8-inch). To install the new studs, we checked and adjusted the guideplate alignment before torquing down each stud.

For Test 6 we installed a High Velocity Heads (HVH) 2-inch carb spacer and S&B 4x15-inch air filter. This combo netted our best power of the day at 523 hp at 6,200 rpm. The HVC carb spacer is a four-hole unit that transitions into one large opening before the air/fuel mixture enters the intake manifold. This improves velocity.

We tagged along as Thomson builds an affordable small block race engine for a Cheap Street competitor, while making sure that it makes 600 hp and will last the entire race season. - Super Chevy Magazine » Read More